Gene therapy treatments are rapidly becoming a reality, with several dozen gene therapy protocols approved by the National Institutes of Health, many of which being currently underway.
There are a number of ocular diseases and conditions which could be suitable for treatment with ocular gene therapy. These diseases fall into two categories, ocular disease caused by a specific genetic disorder, whether dominant or recessive, and diseases which have no currently known genetic basis but instead could be treated with the introduction of genes expressing proteins useful in the treatment of the condition.
In the first category, there are a number of diseases for which the underlying genetic defect is known. Autosomal retinitis pigmentosa, both dominant and recessive, may be caused by as many as 50 different mutations in the rhodopsin gene (Bok, Invest. Ophthalm. and Visual Sci. 34(3):473 (1993)). Autosomal dominant retinitis punctual albescens, butterfly-shaped pigment dystrophy of the fovea, and adult vitelliform macular dystrophy, have been correlated to a mutation in the peripherin/RDS gene (Kajiwara et al., Nature Genetics 3: 208 (1993); Nichols et al., Nature Genetics 3:202 (1993); Wells et al., Nature Genetics 3:213 (1993)). Norrie's disease (Berger et al., Nature Genetics 1:199 (1992)), blue cone monochromasy (Nathans et al., Science 245:831 (1989)), and choroideremia (Cremers et al., Nature 347:674 (1990); Merry et al., Proc. Natl. Acad. Sci. USA 89:2135 (1992)) have all been shown to be caused by genetic mutations. The gene for gyrate atrophy involves more than 60 different mutations in the mitochondrial enzyme ornithine aminotransferase (Bok, supra).
In addition to the diseases for which specific genetic mutations are known to cause the phenotype, there are a number of diseases for which the specific genetic component is unknown. These diseases may have a genetic basis or may be caused by other factors resulting in changes in protein expression. For example, age-related macular degeneration is a significant ocular disease among older patients. Retinoblastoma, anterior and posterior uveitis, retinovascular diseases, cataracts, inherited corneal defects such as corneal dystrophies, retinal detachment and degeneration and atrophy of the iris fall into this category, as do retinal diseases which are secondary to glaucoma and diabetes, such as diabetic retinopathy.
Finally, there are a number of conditions which are not genetically based but are still significant ocular diseases. For example, viral infections such as Herpes Simplex Virus (HSV) or cytomegalovirus (CMV) infections frequently cause significant symptoms, and may cause blindness. Retinal detachment, diabetic retinal disease, retinal vein thrombosis, retinal artery embolism, allergic conjunctivitis and other ocular allergic responses, dry eye, lysosomal storage diseases, glycogen storage diseases, disorders of collagen, disorders of glycosaminoglycans and proteoglycans, sphinogolipodoses, mucolipidoses, disorders of amino aicd metabolism, dysthyroid eye diseases, antierior and posterior corneal dystrophies, retinal photoreceptor disorders, corneal ulceration and other ocular wounds such as those following surgery are also significant conditions which do not have a known genetic component.
Recent work has shown that the retinal degeneration phenotype of the rd mouse, which has served as a model for the study of human retinitis pigmentosa for over 30 years, may be rescued by the expression of a bovine cGMP phosphodiesterase B-subunit in transgenic rd mice (Lem et al., Proc. Natl. Acad. Sci. USA. 15:442 (1992)). Similarly, the retinal degeneration slow (rds) phenotype of the rds mouse may also be corrected by the creation of transgenic mice expressing the wild-type rds gene product, a 39 kD membrane-associated glycoprotein (Travis et al., Neuron, 9:113 (1992)). However, as pointed out by several commentators, transgenic techniques are not directly applicable to human therapy, due to the uncertainties of transgene insertion (Zack, Arch. Ophthalmol. 111:1477 (1993), Bok, supra).
Additionally, in vitro gene transfer using a retroviral vector has been done on cells deficient in .beta.-glucoronidase, an enzyme deficiency which is inherited in an autosomal recessive manner. After transformation with the gene coding for the enzyme, the .beta.-glucuronidase deficient cells exhibited normal enzyme activity (Stramm et al., Exp. Eye Res 50:521-532 (1990)).
Recently, two in vivo protocols using adenoviral vectors have been reported. Bennett et al., Investigative Ophtahalmology and Visual Science, 1994, 35(5):2535; Li et al., Investigative Ophtahalmology and Visual Science, 1994, 35(5):2543.
Therefore, there is a need for in vivo and in situ ocular gene therapy. Accordingly, it is an object of the invention to provide methods for the generation of genetically-engineered ocular cells, and specifically, methods for the generation of genetically-engineered in situ ocular cells.